1 . Field of the Invention
The present invention relates to an electrocardiogram (ECG) signal processing apparatus and in particular to an apparatus useable in conjunction with known ECG monitors to extract signals from ECG signals, for example atrial fibrillation signals, in which the effects of ventricular activity have been suppressed.
2 . Description of the Prior Art
ECG technology is well established as a means for studying the function of the heart and identifying disorders of the heart. One disorder that may be studied by ECG is atrial fibrillation. It is known to facilitate the detection and characterization of atrial fibrillation in the surface ECG signal by the use of a signal, the so called "residual ECG signal," in which the ventricular activity has been first cancelled to leave the atrial signal. Such cancellation techniques have earlier been implemented by subtraction of an average QRST complex from each individual beat (J. Slocum et al. "Computer Detection of Atrioventricular Dissociation from Surface ECG During Wide QRS Complex Tachycardia" Circ., 72: 1028-1036, 1985). Due to the single lead nature of this so called "average-beat" approach, variations in the electrical axis of the heart may sometimes cause large QRS-related residuals which render the subsequent analysis of atrial fibrillation more difficult.